Up to now, an electric power steering device having two systems of torque sensors has been known. For example, in Patent Literature 1, when an abnormality of one of the torque sensors is detected, a steering assist control is continued with the use of a steering torque detected by the torque sensor where no abnormality is detected.
In Patent Literature 1, a torque sensor in which an abnormality occurs is identified based on a deviation between a detection value and an estimated torque of the torque sensor. In addition, excessive assist is prevented by setting an upper limit value of a target assist torque based on the deviation between the detection value and the estimated torque of the torque sensor.
However, in Patent Literature 1, when an abnormality of one of the torque sensors is detected, an abnormality detection cannot be performed by comparing the detection values of both the torque sensors with each other, and the abnormality detection accuracy may be lowered.